Label-free identification of tumor tissues by coherent nonlinear vibrational mode imaging

Abstract

A multimodal hyperspectral vibrational sum-frequency generation (VSFG) platform and a method of tumor diagnosis are provided. The method employs the chemical-specific VSFG microscopy platform as a label-free imaging technique for tumor identification.

What is claimed is: 
     
         1 . A multimodal hyperspectral VSFG microscope platform, comprising:
 a pulsed laser beam;   an optical parametric amplifier (OPA), configured to guide the output of the laser beam, generating a mid-infrared (MIR) beam;   a Fabri-Perot etalon, configured to pass the residue laser beam from the OPA for an up-conversion near IR (NIR) beam;   a dichroic mirror (DM), wherein the MIR beam and the NIR beam are spatially overlapped;   a resonant beam scanner mounted to an integrated 2-position slider (I2PS);   an inverted microscope configured to integrate with the beam scanner, wherein the MIR beam and the NIR beam are overlapped and are directed into the inverted microscope;   a reflective-based infinity-corrected Schwarzschild objective (SO) and a refractive-based infinity-corrected imaging objective (RO) mounted to a vertical nanopositioning (VNP) z-axis stage;   a microscope stage for retaining a sample, mounted between the SO and the RO, whereby overlapped beams from SO are focused onto the sample and a VSFG signal generated by the sample is collected by RO;   a linear polarizer and a telecentric tube lens system, whereby the signal is guided through and processed;   a monochromator (MC), wherein a magnified image formed at the entrance slit of the MC; and   a charge-coupled device (CCD) coupled with the linear polarizer and the telecentric tube lens system, whereby a magnified image and data are detected and collected.   
     
     
         2 . The platform of  claim 1 , wherein the laser beam having ˜100 fs time duration; 
     
     
         3 . The platform of  claim 1 , wherein the DM is transmissive to the MIR and reflective to the NIR. 
     
     
         4 . The platform of  claim 1 , wherein the SO is purely reflective, acting as a condenser. 
     
     
         5 . The platform of  claim 1 , wherein the z-axis position of the RO is controlled at 1 μm precision. 
     
     
         6 . The platform of  claim 1 , wherein the tube lens system comprises two tub lenses (TL 1  and TL 2 ). 
     
     
         7 . A method for detecting tumor in a biological tissue sample with the VSFG microscope platform of  claim 1 , comprising:
 mounting the tissue sample on a slide to the microscope stage;   subjecting the tissue sample with NIR and MIR beams using Objective 1 (OL1) of the microscope;   turning on the resonant beam scanner to raster the laser beams on the tissue samples;   collecting a resulting VSFG signal using Objective 2 (OL2) of the microscope;   directing the VSFG signal to a spectrometer and a CCD; and   obtaining VSFG hyperspectral images, whereby the tumor is detected.   
     
     
         8 . The method of  claim 7 , wherein the biological tissue sample comprises collagen. 
     
     
         9 . The method of  claim 7 , wherein the biological tissue sample is derived from lung tumor, breast cancer, colorectal liver metastases, esophageal squamous cell carcinoma, or malignant ovarian neoplasms. 
     
     
         10 . A method for detecting tumor in a biological tissue sample with the VSFG microscope platform of  claim 1 , comprising:
 mounting the tissue sample on a slide of the microscope stage;   subjecting the tissue sample with NIR and MIR beams using Objective 1 (OL1) of the microscope;   turning on the resonant beam scanner to raster the laser beams on the tissue sample;   collecting a resulting VSFG signal using Objective 2 (OL2) of the microscope;   directing the VSFG signal to a spectrometer and a CCD;   obtaining VSFG hyperspectral images; and   analyzing spectral signatures of the images for a NH S /CH 2,Ss  and   CH S /CH 2,Ss  ratio mapping wherein the tumor is detected.   
     
     
         11 . The method of  claim 10 , wherein the biological tissue sample comprises collagen. 
     
     
         12 . The method of  claim 10 , wherein the biological tissue sample is derived from lung tumor, breast cancer, colorectal liver metastases, esophageal squamous cell carcinoma, or malignant ovarian neoplasms. 
     
     
         13 . The method of  claim 12 , wherein the biological tissue sample is derived from lung tumor.